Pd-based bimetallic catalysts for HET-PHIP

Abstract

Abstract. Production of hyperpolarized catalyst-free gases and liquids by heterogeneous hydrogenation with parahydrogen (HET-PHIP) can be useful for various technical as well as biomedical applications, including in vivo studies, investigations of mechanisms of industrially important catalytic processes, enrichment of nuclear spin isomers of polyatomic gases, and more. In this regard, the wide systematic search for heterogeneous catalysts effective in pairwise H2 addition required for the observation of PHIP effects is crucial. Here in this work we demonstrate the competitive advantage of Pd-based bimetallic catalysts for HET-PHIP. The dilution of catalytically active Pd with less active Ag or In atoms provides the formation of atomically dispersed Pd1 sites on the surface of Pd-based bimetallic catalysts, which are significantly more selective toward pairwise H2 addition compared to the monometallic Pd. Furthermore, the choice of the dilution metal (Ag or In) has a pronounced effect on the efficiency of bimetallic catalysts in HET-PHIP, as revealed by comparing Pd-Ag and Pd-In bimetallic catalysts.

Pd on Nanodiamond/Graphene in Hydrogenation of Propyne with Parahydrogen

“…The exploration of SACs in this context is a viable approach since SACs provide a useful bridge between homogeneous and heterogeneous catalysis . One promising type of catalyst on the way to SACs is bimetallic catalysts, in which the metal active in the hydrogenation is diluted with catalytically inert or less active atoms . Pd–Au, , Pd–Ag, Pd–In, and Pt–Sn catalysts were recently investigated in terms of PHIP; for Pt–Sn catalysts, a pairwise selectivity of 10.9% was observed, but the overall conversion was estimated only as 0.5% .…”

“…One promising type of catalyst on the way to SACs is bimetallic catalysts, in which the metal active in the hydrogenation is diluted with catalytically inert or less active atoms . Pd–Au, , Pd–Ag, Pd–In, and Pt–Sn catalysts were recently investigated in terms of PHIP; for Pt–Sn catalysts, a pairwise selectivity of 10.9% was observed, but the overall conversion was estimated only as 0.5% . The progress of catalyst design in the context of HET-PHIP is covered in recent reviews. , …”

Recent advances in the application of parahydrogen in catalysis and biochemistry

“…145,147,148 In recent years there is a growing number of studies, where metal-nanoparticles or other heterogeneous catalysts were employed for the generation of PHIP hyperpolarized gases like propene. 38,56,149–172 A major driving force for these developments is the search for the cost-efficient production of hyperpolarized gases for contrast enhancement in medical applications of NMR such as MRI imaging of the lung, as PHIP does not depend on expensive additional hardware and is thus more amenable to implementation in medical diagnostics. 173–175…”